Organosiloxanes containing trifluoromethylphenyl groups



Patented Apr. 28, 1953 ORGANOSILOXANES CONTAINING TRIFLU-OROMETHYLPHENYL GROUPS Lawrence W. Frost, Pittsburgh, Pa., assignor toWestinghouse Electric Corporation, East Pittsburgh, Pa., a corporationof Pennsylvania No Drawing. Application September 29, 1949, Serial No.118,718

6 Claims. 1

This invention relates to organosilicon compounds containing fluorineand in particular or- 'ganosilicon compounds containing polyfiuoroorganic substituents attached to silicon.

This application is a continuation in part of my copending applicationSerial No. 751,964, filed June 2, 1947, now abandoned.

The object of this invention is to prepare organosilicon compoundscontaining polyfluoro organic substituents attached to silicon.

Another object is to provide methods for introducing polyfiuoro organicgroups into organosilicon compounds.

A further object of the invention is to provide siloxanes in whichtrifiuoromethyl substituted phenyl radicals are attached to silicon.

A still further object of the invention is to provide for heathardenable polysiloxane resins containing trifiuoromethyl radicalsattached to silicon through intervening carbon groups.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The present invention is based on the discovery that p-olyfluoro organicsubstituents may be attached by hydrocarbonsilicon linkages to siliconin organosilicon compounds. These compounds, if provided with ahydrolyzable group, may be subsequently treated to produce polysiloxanesin which polyfiuoro organic groups are attached to silicon bycarbonsilicon linkages. A number of methods may be employed inintroducing the polyfluoro organic substituents into organosiliconcompounds. One effective method is to prepare chlorosilanes and to treatsuch chlorosilanes by means of a fiuorinating agent to replace chlorinewith fluorine. The following general processes are exemplary.

(ether) g R (CFs) MgBr R is a phenylene radical. In the above equations3 and 4, the bromine attached to the phenylene radical may be replacedwith chlorine or iodine.

Fluorine-containing organosilicon compounds produced as disclosedherein, which also contain a hydrolyzable group, for example, a halideor alkoxy group, attached to silicon, may be subsequently subjected tohydrolysis and polymerization with formation of either fluid or solidpolyiiuoropolysiloxanes. In some cases the fluorinecontainingorganosilicon compounds may be condensed with other organosiliconcompounds thereby producing interpolymer compounds containing polyfiuoroorganic groups in predetermined proportions. The hydrolyzablepolyfiuorosilicon compounds or their low polymers behave in manyrespects much as do non-fluorine containing conventional organosiliconcompounds with regard to hydrolysis and condensation reactions. However,the polymers have certain other distinctive properties which render themhighly useful. One outstanding characteristic appears to be a greatlyimproved thermal resistance possessed by the siloxane polymers andcopolymers containing a plurality of fluorine atoms attached to carbon.Thus, films of the polyfluorosiloxanes will withstand highertemperatures, other conditions being equal, than non-fluorinecontainingpolysiloxanes. In many cases the solid fluorine-containing polysiloxanesare harder and tougher. Other advantages of the fluorinecontainingpolysiloxanes as Well as the intermediates will be describedhereinafter.

More specifically, my invention comprises the preparation ofhydrolyzable silanes having attached to silicon from 1 to 3 substitutedphenyl groups wherein the substituents comprise one or moretrifluoromethyl radicals. The trifluoromethyl groups may be substitutedortho, meta or para on the phenyl groups. Two or three trifluoromethylgroups may be attached to the phenyl radicals in various positions.Silanes may be readily prepared with several different substitutedphenyl radicals attached to the central silicon atom, some of the phenylgroups being provided With one, others with two or three trifluoromethylgroups attached in substantially any position on the phenyl radical.Mixed silanes, comprising a mono trifiuoromethyl phenylsilane and abis(trifiuoromethyl)phenylsilane or tris(trifluoromethyDphenylsilane maybe produced. Such compositions comprise at least one compound having theformula radical selected from the group consisting of chlorine, fluorineand alkoxy radicals, and n and a: each represents a number from 1 to 3.

The silanes may include phenyl or methyl groups or both attacheddirectly to silicon in conjunction with trifluoromethylpheny1 radicalsalso attached to silicon. Likewise, it is a feature of the invention toprepare silicon compounds wherein a trifluoromethylphenyl group isattached to one silicon atom and an alkyl, aryl, cycloalkyl, alkaryl orother monovalent organic group is attached to another silicon atomconnected to the first silicon atom by an oxygen linkage. Examples ofsuch monovalent radicals are methyl, ethyl, propyl, isobutyl, octyl,dodecyl, cyclohexyl, allyl, methallyl, phenyl, tolyl, xylyl and naphthylradicals. Examples of hydrolyzable radicals that may be attacheddirectly to silicon are chlorine, bromine, fluorine, methoxy, ethoxy,and propoxy.

In order that those skilled in the art may betterunderstand theinvention, the following specific. examples are given.

EXAMPLE I Preparation of 3-(trifluor0methyl)phenylsilanes Thepreparation of (trifluoromethyDphenylethoxysilanes was accomplished asfollows: A solution of 255 g. of 3-bromo-(trifluoromethyl) benzene in200 ml. of absolute ether was added slowly to 25 g. of finely dividedmagnesium metal, 100 ml. of absolute ether and a crystal of iodine, allwithin a closed reaction vessel provided with areflux column. Themixture was slightly heated to initiate reaction. Once started, the

reaction proceeded readily and maintained a steady reflux withoutexternal heating. When the addition was complete, the solution wasdiluted to a total volume of 1 liter with anhydrous ether. The clearsolution was then added slowly with stirring to 166.4 g. of ethylorthosilicate. The mixture was refluxed during the addition and for hr.thereafter. The mixture was then distilled to remove ether; toward theend of the distillation, benzene was added to enable the removal of thelast of the ether. The remaining liquid was filtered to remove salts andthe salts were washed thoroughly with benzene. The washings and thefiltrate were combined and 'fractionally distilled. The resultingfractional distillation produced 43 g. of ethyl orthosilicate, 39.5 g.of 3-(trifiuoromethyl)phenyltriethoxysilane (B. P. 86.5" C. to 875 C. at4 mm.) 46.5 g. of bisE3-(trifluoromethyl) phenyl] diethoxysilane(boiling point 104 C. to 115 C. at 1 mm.), and 14 g. of a higherboiling-point liquid which appeared to be a mixture of the triandtetrasubstituted trifluoromethylphenyl silicon compounds.

EXAMPLE II Bisl3- (trz'flum-omethyl) phenyl] siloranes The bis [3-(trifluoromethyl) phenyl] diethoxysilane from Example I was purified byrepeated crystallization at low temperatures. A white crystallinematerial, melting at 20 0., Was obtained. Aportion, comprising 4.3 g.,of the white crystalline material was boiled for 3 hours with a mixturecomposed of ml. each of toluene, water, concentrated hydrochloric acidand 95% ethanol to hydrolyze it. A non-aqueous layer which carried thesilicon compound was decanted. The organic layer was washed twice Withwater and then heated for hours at 110 C. to drive off the volatiles. Anoil remained 4 after this treatment. After further heating at 250 C. for2 hours, the product increased in viscosity considerably but still wasan oily fluid in an amount of 3 g. The composition of the oil wasdetermined to be:

where n had a-value greater than 10, and the trifluoromethyl groups werein the meta position. Both cyclic and linear oily polymers are formed.Low viscosity fluids with the above formula result where n is 4 orhigher. In the linear polymers the chains terminate in silicon atomswith three monovalentsubstituent groups. The three monovalent groups maybe trifluoromethylphenyl radicals.

EXAMPLE III Silomane copolymers of 3-(trifluoromethyllphenylsilanes Asiloxanev copolymer of the product of Example I was prepared as follows:A mixture composed of 2.643 g. of methyltriethoxysilane, 2.169 ofdimethyldiethoxysilane, 2.26.4 g. of 3-(trifluoromethyl) phenyltriethoxysilane and'3.041 g. of his [3- (trifluoromethyl) phenyl]diethoxysilane was dissolved in 25 ml. of toluene. The solution soproduced was added slowly with stirring to 50 ml of 5% sulfuric acid.After the mixture was stirred and refluxed for 3 hours, the'organiclayer was separated, washed with Water several times and then addedslowly to 50 ml. of 40% sulfuric acid. The mixture was stirred at roomtemperature for 2 hours and then allowed to stand to permit an organiclayer to separate out. The organic layer was decanted, washed out withbarium hydroxide solution followed by washing in water, and then driedover sodium sulfate. The relatively anhydrous solution so .produced wastransferred to an aluminum dish and heated atl75 C. for 5 hours. A lightyellow, flexible film, approximately of an inch thick, was formed at thebottom of the aluminum dish. It was heated in contact with theatmosphere for 8 hours at 250 C. beforeany oracleing of the film wasapparent, A'similar copolymerhaving a similar proportion of phenylgroups in place of the (trifiuoromethyl) -phenyl groups, prepared in thesame Way and of the-same thickness cracked after 5 hours at C. Thethermal stability of the copolymer containing trifluoromethyl groupssubstituted on phenyl was markedly superior to that of the copolymerhaving no trifluoromethyl groups.

EXAMPLE IV Preparation of 4-(trifluoromethg Z) phenylsz'lanes 492 partsby weight of liquid 4-methylphenyltrichlorosilane was exposed to actiniclight while dry chlorine was bubbled therethrough. After an inductionperiod, hydrogen chloride was evolved and the liquid became colorless.During the chlorination,- the temperature of-the liquid :roseexothermallyto 65 C., and chlorine was added at a rate to keep theproduct at this temperature over a period of 8 hours. Thereafter, thetemperature was raised to between 90 C. and 100 C., and chlorination wascontinued at this temperature for an additional 18 hours. When theresulting reaction product was cooled to room ternperature, itsolidified. The resulting crude 4-(trichloromethyl)phenyltrichlorosilane so produced weighed 691 parts. Aportion of the product was recrystallized from anhydrous ethyl ethertwice to produce a substantially pure silane which was in the form ofcolorless needles having a melting point of 67.5 to 68 C.

A mixture of 99 parts of the crude 4-(trichloromethyl)phenyltrichlorosilane and 23 parts of antimonypentachloride was stirred rapidly while 127 parts by weight of powderedantimony trifluoride was added thereto slowly. Heat was evolved duringthe addition. After all of the antimony fluoride had been added, themixture was heated to a higher temperature and a distillate fractioncomprising 51 parts by weight of a colorless liquid product was obtainedwhich on being subjected to redistillation produced relatively pure 4(trifluoromethyl)phenyltrifluorosilane boiling over a 2 C. range. Onfurther purification, a sample of this last distillate was found to havethe following physical constants: boiling point ll8.'7 C.; melting point3 to l C.; n 1.3783; and 114 1.399.

Other fluorinating agents may be used in this process to replacechlorine with fluorine, these include hydrogen fluoride cobalt fluorideand silver difluoride.

EXAMPLE V Preparation of 3-(triflaoromethyl) phenylchlorosilanes Asolution of 225 parts by weight of 3-bromo- (trifluoromethyl) benzenedissolved in 180 parts by weight of anhydrous ethyl ether was addedslowly, with vigorous stirring, to 24 parts by weight of magnesiumturnings. The magnesium dissolved in the solution to produce a darkbrown solution of Grignard reagent. This reagent was added to 340 partsby weight of tetrachlorosilane dissolved in 180 parts of anhydrousether. The reaction flask was cooled in an ice bath during the additionof the Grignard reagent. The reaction mixture was refluxed with rapidstirring for 9 hours. After this period, the liquid was permitted tostand until the salts which had formed had settled and then the liquidwas decanted. The salts were washed twice with toluene, and the washingswere added to the liquid previously decanted. The liquid mixture wasthen fractionally distilled to remove the ether, unreacted silicontetrachloride and toluene. The residue was rectified at a reducedpressure producing 62 parts by weight of 3-(trifluoromethyl)phenyltrichlorosilane having a boiling point of 98 C. at mm., and 46parts of bislB-(trifluoromethyl) phenyl] dichlorosilane having a boilingpoint of 1 0 C. at 3 mm.

EXAMPLE VI Preparation of 3-(triflu0romethyl) phenyltriflaorosilane Amixture of 203 parts by weight of 3- (trifluoromethyl)phenyltrichlorosilane, from the preceding example, and 160 parts byweight of powdered antimony trifluoride was stirred and warmed gently toreflux which was maintained for hour. After refluxing, the mixture wasfractionally distilled to produce a liquid product boiling at from 113C. to 118 C. The product weighed 153 parts by weight. By additionalfractional distillation, a purified sample of3-(trifluoromethyl)phenyltrifluorosilane was secured. Its physicalconstants were: boiling point 118.2 C.; melting point -34 C.; 11.1.3783; and (Z4 1.3985.

Other fluorinating agents capable of replacing chlorine with fluorinemay be substituted for the antimony trifluoride, and examples of theseare silver fluoride, hydrogen fluoride, bromine fluoride and cobaltfluoride.

EXAMPLE VII Preparation of Z-(trz'fluoromethyl)phenyldimethylchlorosilane A solution of 5 moles of n-butyllithium in 3liters of anhydrous ethyl ether was prepared, and to this solution wasadded 584 grams of dry trifiuoromethylbenzene. The mixture was stirredat room temperature for two hours and then refluxed gently with stirringfor 16 additional hours. The resultant slurry was added slowly withstirring to 645 grams of dimethyldichlorosilane. The resulting mixturewas refluxed with stirring for two hours and then filtered to remove thesalts. The filtrate was distilled at atmospheric pressure to removeether and unreacted dimethyldichlorosilane. Distillation was thencontinued at a reduced pressure to produce a fraction comprising 135milliliters of crude 2-(trifluoromethyl) phenylolimethylchlorosilane.Upon redistillation to give a relatively pure product, the compound wasfound to have a boiling point of 78 C. at 12 mm.

The process of this Example VII may be carried out by substituting otherdichlorosilanes for the dimethyldichlorosilane. Thus phenyl-methyldichlorosilane, diphenyldichlorosilane and other dialkyl-, diarylandary1alkyl-, dichlorosilanes may be substituted in whole or in part forthe dimethyldichlorosilane. There will result silanes with onetrifluoromethyl phenyl radical and two non-fluorinated radicals attachedto a common silicon atom.

EXAMPLE VIII Hydrolysis 0 (triflaoromethyl) phenyltrifluorosilanes The(trifluoromethyl)phenyltrifluorosilanes of Examples IV and VI were eachhydrolyzed in the following manner. An 0.038 mole sample of the silanewas dissolved in 50 milliliters of toluene. The solution was addedslowly to a well stirred refluxing mixture comprising 50 milliliters ofwater, 50 milliliters of ethanol and i0 milliliters of concentratedhydrochloric acid. The mixture was stirred and refluxed for anadditional 18 minutes after combination. The mixture was then agitatedwith milliliters of water and then permitted to separate into twolayers. The non-aqueous layer was decanted and placed in an oven at atemperature of 100 C. for 16 hours to evaporate the organic solvent. Anoily residue resulted which was then heated at 200 C. The productderived from 4- (trifluoromethyl)phenyltrifluorosilane was converted toa hard brittle solid in 5 hours. It was soluble in toluene but becameinsoluble after further heating at 200 C. The product from thehydrolysis of B-(trifluoromethyl) phenyltrifluorosilane was convertedonly to a soft thermoplastic material even after heating for 24 hours at200 C. Further heating caused the product to harden slowly. However, itwas still completely soluble in cold toluene after 1325 hours baking at200 C.

Hydrolysis of 3-ct'rz'fluoromethyl)phenz/Z trichlorosilane Following theprocedure oftheprevious example, samples of. S-(trifluoromethyi)phenyltrichlorosilane were hydrolyzed and condensed. The productproduced after the preliminary baking 1'01 16' hours at 100 C was a softsolidresini body which was tack-free at room temperature. After anadditional baking for 2.4 hours at 200 0., the siloxane resin had becomemuch harder and was somewhat-brittle. It dissolved in toluene.

Mixtures of any two orall three of the mono-(trifluoromcthyl)phenylsilanes in which'the trii uoromethylgroup isortho, meta and para to the silicon atom and the remaining valences ofthe silicon atom are satisfied by hydrolyzable groups, may be hydrolyzedand condensed as set forth in. Example VIII, to produce resinoussiloxa-nes.

Hydrolysis of bis [3.- (,irifluoromctiwl) phenyl] dichloroszl'ane A.solution of 62 grams of bisl3-(trifluorometlryl) phenyll dichlorosilaneO milliliters of toluene was added. slowly to a well stirred refluxingmixture comprising 58 milliliters of water, milliliters of 95%v ethanoland, ill-milliliters of concentrated hydrochloric acid. The mixture wasrefluxed with stirringfor 1 hour after which the mixture was permittedto stand and form two layers. The non-aqueous layer was removed washedwithwater; The non-aqueous layer was then stirred for 1. hour". at room.temperature with 150 milliliters of 50.5% sulphuric acid. Afterstanding, the organic layer, which formed, was separated and washed,first with a sodium bi carbonate solution andthsn with distilled Water.The washed. organic solution was filtered and then placed in an oven at109 C. for. 64 hours to drive ofi the organic solvent. The. oilysiloxane resulting was: transferred to an oven at 2003 C. for 1 hour.The product consisted of 49 of a light yellow oil. Further baking at 200C. for '72 hours While exposed to the atmosphere produced no furtherapparent change except for aslight increase in viscosity. The formulafor the product was similar to that shown in Example II.

Similar oils resulted when the bislZ-(trifluoromethyl) phenyl] silaneand bisl l-(trifluoromethylDphenyllsilanes with two hydrolyzablesubstituents on each silicon atom were hydrolysed and condensed.Mixtures of these compounds having the trifluoroinethyl groups invarious positions on the two substituted phenyl groups on each siliconatom will produce stable fluids.

In a similar manner to that set forth in EX- ainple- IV,xylylchlorosilanes may be chlorinated to replace the hydrogen atoms onthe methyl groups in the Xylyl radical and then fluorinate'd to producebis (trifluoromethyl) phenylfluorosilanes which may be hydrolyzed andcondensed by the procedure of Example VIII into apolyfluoropolysiloXane.v From one to three bis(trifluoromethyDpheny-ligroups may be attached to a: silicon atom.

Depending; upon-their. structure, the fluorinecontainingorgano-polysiloxanes may be in the form. of fluids or solids; The stablefluids will be found to be non-cross-linked cyclic or linear structures,or a mixture of both, containing on the average-approximately twoorganic groups, preferably substituted phenyl groups with at leastone.trifluoromethyl substituent, directly connected to each silicon atom,the other silicon bonds being connected to oxygen. In case of linearstructures, the fluids may have a. terminal structure wherein. threemonovalent, non-hydrolyzable, organic groups are connected to the lastsilicon atom. By proper reaction conditions, fluids may be secured witha wide range of viscosities; By fractional distillation of such fluids,fractions of almost any required viscosity may be obtained'. Theviscosity-temperature curves of the. fluids are much flatter than thoseof ordinary petroleum. lubricants. The polyfluorosiloXa-ne fluids may beemployed. as lubricants, hydraulic fluids; sealing compounds for plugcocks. and heat transfer fluids. They may be used as fluid dielectrics;Their thermal and chemical. stability render. them highly suitable forthese and. other app c o Cross-linked polysiloxanes containingpolyfluoro' organic groups may be prepared and employedin variouscapacities. They will average from one to less than two organicsubstituents per silicon atom- When incompletely condensed, they areliquids or gels that be hardened by: heat treatment and'the addition ofcatalysts into solids varying from rubbery to hard, brittle bodies. The:solidifiable compositions may be employed for electrical. insulation, aspaints, coating compositions, bonding. agents for mica flakes and formetal, and the like. For any given application 2. suitable hardenablecomposition may be selected. Usually, a low polymer or incompletelycondensed siloxane in a solvent soluble stage is employed forapplication to a base member and is. owed to a final hard solidcondition: after being applied and the solvent driven off; The partiallycondensed polyiluoropolysiloxane may be dissolved in organic solventssuch as toluene, Xylene orthe: like, to a suitable: viscosity fluid soas to be readily applied to members; Alternatively, the siloxane maybeadmixed while in a fluid or gelatinous: state: Witlivari'ous fillerssuch, for example, as powdered: inorganic solids. or fine fibers such asglass fibersv and asbestos,- carbon, iron oxide, silica and thelike, andmoldedlinto' members and cured under heat. to a; solid state. Laminatesor other bodies: reinforced with asbestos or glass fiber fabrics? can bemade from polyiluorosiloxanes;. To. enable: curing to a solid state, theintermediatefsiloxanes may be admixed with catalysts, particularly"organoinetal compounds of monovalenti organic acids commonly used asdriers, such". for example as lead octoate, lead naphthenote andcobalt'linoleate, and then heat-treated;

Numerous other uses of the invention will be obvious to. thoseskill'ed;in. the art, and it is desired that the specification be-int'erpreted asillustratilve and notin alimiting sense.

I claim: as my invention 1. A fluorosiloxane having the generalformula:

2. A fluid fiuorosiloxane having the general formula:

[0 FsCaH4]=-Sl where x is a number from 1 to 2.

5. A siloxane copolymer having Si-OSi linkages and with organic groupsattached to the silicon atoms by carbon silicon linkages, the or anicgroups attached to a portion of the silicon atoms consisting of CF3CeH4groups, while the organic groups attached to the remaining silicon atomsconsist of a radical selected from at least one of the group consistingof methyl and. phenyl radicals.

6. A siloxane copolymer having Si--O'--Si linkages and with organicgroups attached to the silicon atoms by carbon silicon linkages, theorganic groups attached to a portion of the silicon atoms consisting ofCF3CsH4 groups, while the organic groups attached to the remainingsilicon atoms consist of monovalent hydrocarbon radicals.

LAWRENCE W. FROST.

References Cited in the file of this patent McBee et al., Industrial andEngineering Chem, vol. 39, No. 3, March 1947.

6. A SILOXANE COPOLYMER HAVING SI-O-SI LINK AGES AND WITH ORGANIC GROUPSATTACHED TO THE SILICON ATOMS BY CARBON SILICON LINKAGES, THE ORGANICGROUPS ATTACHED TO A PORTION OF THE SILICON ATOMS CONSISTING OF CF3C6H4GROUPS, WHILE THE ORGANIC GROUPS ATTACHED TO THE REMAINING SILICON ATOMSCONSIST OF MONOVALENT HYDROCARBON RADICALS.